Problem: Subtract.
There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of tenths: $\begin{aligned} &\phantom{=}5.7 - 3\\\\ &=5.7 - 3.0\\\\ &=57\text{ tenths} - 30\text{ tenths}\\\\ &=27\text{ tenths}\\\\ &=2.7 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Ones $.$ Tenths ${5}$ $.$ $7$ ${3}$ $.$ $0$ Now, let's subtract each place value column. Ones $.$ Tenths ${5}$ $.$ $7$ $-$ $3$ $.$ $0$ $\underline{~~~~}$ $\underline{~~~~}$ $2$ $.$ $7$ $2.7 = 5.7 - 3$